1. Field of the Invention
The present invention relates to a desensitizing dentifrice composition which eliminates or reduces the discomfort and pain associated with dentinal hypersensitivity and more particularly to a two-component desensitizing dental composition containing tin salt and potassium salt desensitizing agents.
2. The Prior Art
Dentinal hypersensitivity is defined as acute, localized tooth pain in response to physical stimulation of the dentine surface as by thermal (hot or cold) osmotic, tactile combination of thermal, osmotic and tactile stimulation of the exposed dentin.
Exposure of the dentine, which is generally due to recession of the gums, or loss of enamel, frequently leads to hypersensitivity. The art has determined that dentine tubules open to the surface have a high correlation with dentine hypersensitivity, Abs, J. Clin. Periodontal. 14,280-4 (1987). Dentinal tubules lead from the pulp to the cementum. When the surface cementum of the tooth root is eroded, the dentinal tubules become exposed to the external environment. The exposed dentinal tubules provide a pathway for transmission of fluid flow to the pulpal nerves, the transmission induced by changes in temperature, pressure and ionic gradients. Tin salts such as SnF2 have been indicated clinically to be efficacious in the reduction of dentinal hypersensitivity. This latter therapeutic effect is believed to be attributable, to a large degree, to the stannous ion (Sn2+) component of the salt. SnF2 is believed to be effective in desensitization by occlusion of exposed dentinal tubules wherein deposits of low solubility complexes of tin are formed on the surface of exposed dental tubules effectively blocking the openings. When hypersensitive teeth are treated with dentifrices containing tin salts such as SnF2, tin deposits accumulate on the tooth surface with each treatment until complete, or virtually complete, coverage of the exposed dentine tubules occurs. By blocking the dentinal tubules external stimuli have a diminished effect, resulting in less pain.
It is also known to the art that potassium salts are effective in the treatment of dentinal hypersensitivity. For example, U.S. Pat. No. 3,863,006 discloses that toothpastes containing potassium salts such as potassium nitrate desensitize the teeth after tooth brushing for several weeks. It is believed by those skilled in the art that an elevation in the extracellular potassium concentration in the vicinity of pulpal nerves underlying sensitive dentin is responsible for the therapeutic desensitizing effect of topically applied oral products which contain potassium nitrate. Due to passive diffusion of potassium ion into and out of the open dentine tubules, repeated application of the active ingredient is necessary to build up the necessary concentration in the vicinity of the pulpal nerves.
Attempts to include mixtures of desensitizing agents such as SnF2 and potassium salts such as potassium nitrate in a single desensitizing dental composition have been found to be of limited effect as a means for delivering efficacious amounts of both ingredients to the teeth. In the case of tin salts such as SnF2, insoluble stannic salts and stannous compounds such as Sn(OH)2 and SnO2 are formed in the composition during storage, and the insoluble salt is ineffective in occluding the dentin surface to provide the desired desensitizing effect.
U.S. Pat. No. 5,693,314 discloses a two component desensitizing dental composition in which a first dentifrice component contains a desensitizing potassium salt and a second gel component contains a desensitizing stannous salt, the first and second components being maintained separate from each other until dispensed for application to teeth requiring relief from dentine hypersensitivity. It is believed that the improved pain relief obtained from the use of the combination of stannous and potassium salts is due in part to the gradual mineralization on the dentin surface which can either totally or partially occlude dentin tubules. Total occlusion will dramatically reduce fluid flow within the tubules which stimulates pain. Partial occlusion of the dentin tubules is believed to increase delivery of potassium ion inside the tooth because the inward diffusive flux is less dependent upon tubule radius than outward fluid flow (due to positive pulpal pressures). Therefore, this enhanced delivery of potassium should enhance relief.
Although the two component desensitizing dental composition of U.S. Pat. No. 5,693,314 is highly effective in the treatment of dentine hypersensitivity, efforts continue to further enhance the efficacy of this type of composition.
The present invention encompasses a dual component desensitizing dental composition in which the individual components are manufactured separately before use, the individual components when combined and applied to the teeth provide a composition which contains a desensitizing combination of a potassium salt and tin salt desensitizing agent whereby improved pain relief is attained.
The present invention is based upon the discovery that when a water soluble alkaline compound such as NaOH is included in the potassium salt containing dentifrice component at a concentration of about 0.5 to about 15% by weight, the combined composition exhibits improved effectiveness when applied to the teeth in obturating dentinal tubules with concomitant desensitization of teeth as compared to compositions in which the alkaline agent is absent.